There is a demand for increasing the capacity of a storage device for storing data, represented by a magnetic disk device. To meet this demand, the storage density (track density and bit density) of a disk medium is being more and more increased.
In such storage devices, when data has repeatedly been written to a target track as a write target (hereinafter, referred to simply as a target track), a phenomenon (erase phenomenon) occurs, in which data on tracks near the target track will be erased due to, for example, the leakage flux of a head. Because of this phenomenon, if a data write to a particular track (or sector) is repeated, data of adjacent and neighborhood tracks to the particular track will be erased. To avoid this, when the number of data writes to a certain recording area (i.e., a write count) exceeds a predetermined value, processing for rewriting data (i.e., data refresh) is performed. A threshold associated with the write count for data refresh may be beforehand determined for each recording area in a manufacturing process. To overcome the phenomenon that adjacent track data is erased due to an off-track write, there is another known technique of prohibiting writing when the off-track write is exceeded predetermined positioning accuracy (off-track amount) during writing.